Battery pack and thermostat used therefor

ABSTRACT

The present invention reduces components of a circuit board and miniaturizes a battery pack using a thermostat. The battery pack includes a thermostat ( 9 ) having a casing portion ( 10 ) formed of a nonconductive material, a first electrode portion ( 13 ) disposed at one surface ( 10   a ) of the casing portion, and a second electrode portion ( 18 ) and ( 18 ) disposed at another surface ( 10   c ) opposite to the one surface of the casing portion, wherein one electrode lead ( 5 ) projected from a battery cell ( 3 ) is connected to one electrode connecting portion ( 7 ) of a circuit board ( 4 ); another electrode lead ( 6 ) is connected to the first electrode portion of the thermostat; and the second electrode portion of the thermostat is connected to another electrode connecting portion ( 8 ) of the circuit board.

BACKGROUND OF THE INVENTION

The present invention relates to a battery pack and a thermostat usedtherefor, and particularly to a technical field of a battery pack inwhich a battery cell and a circuit board for protecting the battery cellare housed in a casing, and a thermostat used therefor.

There is a battery pack, for example a battery pack in which a lithiumion secondary battery cell is housed in a casing. Such a battery pack isused as a power supply for a communication apparatus such as a portabletelephone, for example.

FIG. 7 and FIG. 8 schematically show an example of a conventionalbattery pack.

A battery pack “a” is formed by housing a battery cell “c” such as alithium ion secondary battery cell or the like and a circuit board “d”for protecting the battery cell “c” within a casing “b”. The batterycell “c” is formed by sealing a battery main body portion “e” with acovering (aluminum laminate material) “f” made of a polymer material.

A first electrode lead “g” connected to a positive electrode of thebattery cell “c” and a second electrode lead “h” connected to a negativeelectrode of the battery cell “c” are projected from the battery cell“c” in the same direction in a state of being separated from each otherat a distance in a direction of width of the battery cell “c”.

The circuit board “d” is provided with a first electrode connectingportion “i”, a second electrode connecting portion “j”, and thermostatconnecting portions “k” and “k”. An end portion of the first electrodelead “g” projected from the battery cell “c” is connected to the firstelectrode connecting portion “i”. An end portion of the second electrodelead “h” projected from the battery cell “c” is connected to the secondelectrode connecting portion “j”.

The circuit board “d” has a thermostat “l” mounted thereon to preventexcessive increase in temperature within the casing “b”. The thermostat“l” has a casing portion “m” formed of a nonconductive material, and apair of electrode portions “n” and “n” projected from the casing portion“m” in directions opposite to each other. The electrode portions “n” and“n” are joined to the thermostat connecting portions “k” and “k”,respectively, of the circuit board “d” by soldering, for example. Thethermostat “l” is situated immediately beside the first electrodeconnecting portion “i”.

The circuit board “d” has required chip parts “o”, “o”, . . . such asICs (Integrated Circuits), FETs (Field Effect Transistors), and the likemounted thereon.

However, the conventional battery pack “a” described above requires thethermostat connecting portions “k” and “k” exclusively for connectingthe thermostat “l” to the circuit board “d”, in addition to the firstelectrode connecting portion “i” and the second electrode connectingportion “j”. Hence there are a correspondingly large number ofcomponents on the circuit board “d”.

In addition, the thermostat “l” needs to be mounted at a positiondifferent from positions of the first electrode connecting portion “i”and the second electrode connecting portion “j” of the circuit board“d”. Accordingly a space exclusively for mounting the thermostat “l” onthe circuit board “d” is required, so that with an increase in size ofthe circuit board “d”, the battery pack “a” becomes larger.

It is accordingly an object of the present invention to provide abattery pack and a thermostat used therefor that overcome the aboveproblems to reduce components of the circuit board and miniaturize thebattery pack using the thermostat.

SUMMARY OF THE INVENTION

In order to solve the above problems, according to the presentinvention, there is provided a battery pack including a thermostathaving a casing portion formed of a nonconductive material, a firstelectrode portion disposed at one surface of the casing portion, and asecond electrode portion disposed at another surface opposite to the onesurface of the casing portion, wherein one electrode lead is connectedto one electrode connecting portion of a circuit board; anotherelectrode lead is connected to the first electrode portion of thethermostat; and the second electrode portion of the thermostat isconnected to another electrode connecting portion of the circuit board.

In order to solve the above problems, according to the presentinvention, there is provided a thermostat for use in a battery pack. Thethermostat includes a casing portion formed of a nonconductive material,a first electrode portion disposed at one surface of the casing portionand connected with another electrode lead, and a second electrodeportion disposed at another surface opposite to the one surface of thecasing portion and connected with another electrode connecting portionof the circuit board.

Thus, in the battery pack and the thermostat used therefor according tothe present invention, one electrode portion of the thermostat functionsas an electrode connecting portion to which one electrode lead isconnected.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an embodiment of a battery pack and a thermostat usedtherefor according to the present invention in conjunction with FIGS. 2to 5, FIG. 1 being a schematic plan view of an inside of the batterypack;

FIG. 2 is a schematic side view of the inside of the battery pack;

FIG. 3 is an enlarged plan view of the thermostat;

FIG. 4 is an enlarged sectional view of the thermostat;

FIG. 5 is an enlarged bottom plan view of the thermostat;

FIG. 6 is a schematic plan view of an inside of another type of batterypack;

FIG. 7 is a schematic plan view of an inside of a conventional batterypack; and

FIG. 8 is a schematic side view of the inside of the conventionalbattery pack.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Embodiments of a battery pack and a thermostat used therefor accordingto the present invention will hereinafter be described with reference tothe accompanying drawings.

A battery pack 1 is formed by housing a battery cell 3 such as a lithiumion secondary battery cell or the like and a circuit board 4 forprotecting the battery cell 3 within a casing 2 of a flat andsubstantially rectangular shape (see FIG. 1). The battery cell 3 isformed by sealing a battery main body portion 3 a with a covering 3 bmade of a polymer material.

A first electrode lead 5 connected to a positive electrode of thebattery main body portion 3 a and a second electrode lead 6 connected toa negative electrode of the battery main body portion 3 a, for example,are projected from the battery cell 3 in the same direction in a stateof being separated from each other at a distance in a direction of widthof the battery cell 3 (see FIG. 1). The first electrode lead 5 is formedof an aluminum material, and the second electrode lead 6 is formed of anickel material.

The circuit board 4 is formed in a rectangular shape that is long in thedirection of width of the battery cell 3. The circuit board 4 has afirst electrode connecting portion 7 and a second electrode connectingportion 8 provided at both respective end portions in a direction oflength of the circuit board 4. An end portion of the first electrodelead 5 projected from the battery cell 3 is connected to the firstelectrode connecting portion 7 by welding, for example (see FIG. 1 andFIG. 2).

The circuit board 4 has a thermostat 9 mounted thereon to preventexcessive increase in temperature within the casing 2 (see FIG. 1 andFIG. 2).

The thermostat 9 is formed in substantially a shape of a rectangularparallelepiped. The thermostat 9 has a casing portion 10 formed of anonconductive material, a first conductive portion 11 formed by aplate-shaped metallic material, and a second conductive portion 12similarly formed by a plate-shaped metallic material (see FIGS. 3 to 5).

The casing portion 10 has a disposing recess portion 10 b that opens ona side of one surface 10 a (see FIG. 4).

The first conductive portion 11 has a first electrode portion 13, amovable piece portion 14, and auxiliary electrode portions 15 and 15(see FIGS. 3 to 5).

The first electrode portion 13 is disposed on the side of one surface 10a so as to cover the disposing recess portion 10 b of the casing portion10. A portion (a portion enclosed by alternate long and short dashedlines in FIG. 3) excluding a peripheral portion of the first electrodeportion 13 is formed as a welding portion area 13 a.

The movable piece portion 14 is formed by bending over from one edge 13b of the first electrode portion 13. The movable piece portion 14 iscapable of elastic displacement with respect to the first electrodeportion 13. The movable piece portion 14 has a contact portion 14 aprovided at an end portion thereof, and the contact portion 14 a isprojected in a direction opposite to a side where the first electrodeportion 13 is situated.

The auxiliary electrode portions 15 and 15 are respectively projectedfrom both side edges orthogonal to the one edge 13 b of the firstelectrode portion 13 in a direction orthogonal to the first electrodeportion 13. The auxiliary electrode portions 15 and 15 have end portionsformed as connecting portions 15 a and 15 a. The connecting portions 15a and 15 a are bent perpendicularly to be parallel with the firstelectrode portion 13, and is situated so as to be opposed to a part ofanother surface 10 c of the casing portion 10. The surface 10 c isopposite to the one surface 10 a of the casing portion 10 (see FIG. 4and FIG. 5).

The second conductive portion 12 includes a base portion 16, connectingportions 17 and 17, and second electrode portions 18 and 18 (see FIG. 4and FIG. 5).

The base portion 16 is buried on an opposite side from the firstelectrode portion 13 in parallel with the first electrode portion 13with the movable piece portion 14 interposed between the first electrodeportion 13 and the base portion 16 within the casing portion 10. Acontact portion 16 a projecting to a side of the contact portion 14 a isprovided at a position opposed to the contact portion 14 a of themovable piece portion 14.

The connecting portions 17 and 17 are formed by being bentperpendicularly from both edges of the base portion 16 in a directionopposite to a side where the first conductive portion 11 is situated.

The second electrode portions 18 and 18 are formed by being bentperpendicularly from both edges of the connecting portions 17 and 17,and are situated so as to be opposed to a part of the other surface 10 cof the casing portion 10 (see FIG. 4 and FIG. 5). The second electrodeportions 18 and 18 are situated so as to be separated from each other ata distance in a direction orthogonal to a direction to connect theconnecting portions 15 a and 15 a of the auxiliary electrode portions 15and 15 with each other (see FIG. 5).

Thus, the second electrode portions 18 and 18 and the auxiliaryelectrode portions 15 and 15 of the thermostat 9 are disposed inside anoutline of the other surface 10 c of the casing portion 10 (see FIG. 5).

A bimetallic disk 19 is disposed between the movable piece portion 14 ofthe first conductive portion 11 and the base portion 16 of the secondconductive portion 12 within the casing portion 10 (see FIG. 4). Thebimetallic disk 19 has one end portion buried in the casing portion 10,and another end portion situated so as to correspond to a position nearan end of the movable piece portion 14.

When due to generation of heat from an outside or the like of thebattery cell 3 and the battery pack 1, the temperature within the casing2 increases and reaches a predetermined temperature, the bimetallic disk19 is bent in a direction to approach the movable piece portion 14, andpresses the movable piece portion 14 in a direction to approach thefirst electrode portion 13, so that the contact portion 14 a of themovable piece portion 14 and the contact portion 16 a of the baseportion 16 in contact with each other are separated from each other.Thus, the first conductive portion 11 and the second conductive portion12 are electrically disconnected from each other to prevent excessiveincrease in temperature within the casing 2.

The circuit board 4 has required chip parts 20, 20, . . . such as ICs,FETs, and the like mounted thereon at a position between the firstelectrode connecting portion 7 and the second electrode connectingportion 8 (see FIG. 1 and FIG. 2).

The second electrode portions 18 and 18 of the thermostat 9 areconnected to the second electrode connecting portion 8 of the circuitboard 4 (see FIG. 1 and FIG. 2). The second electrode portions 18 and 18are connected to the second electrode connecting portion 8 by so-calledreflow soldering performed by melting soldering paste by a hot air,infrared rays, or the like at the same time as the other chip parts 20,20, . . . , for example.

In a state in which the first electrode lead 5 is connected to the firstelectrode connecting portion 7 of the circuit board 4 and the secondelectrode portions 18 and 18 of the thermostat 9 are connected to thesecond electrode connecting portion 8 as described above, an end portionof the second electrode lead 6 is welded and connected to the weldingportion area 13 a of the first electrode portion 13 of the thermostat 9(see FIG. 1 and FIG. 2).

Incidentally, the auxiliary electrode portions 15 and 15 of thethermostat 9 are intended to enable use of the thermostat 9 even in aconventional battery pack by connecting the connecting portions 15 a and15 a of the auxiliary electrode portions 15 and 15 separate from thesecond electrode portions 18 and 18 to a thermostat connecting portionof a circuit board used in the conventional battery pack.

As described above, the battery pack 1 uses the thermostat 9 having thefirst electrode portion 13 disposed in the one surface 10 a of thecasing portion 10 and the second electrode portions 18 and 18 disposedat the other surface 10 c of the casing portion 10. The second electrodelead 6 projected from the battery main body portion 3 a is connected tothe first electrode portion 13, and the second electrode portions 18 and18 are connected to the second electrode connecting portion 8 of thecircuit board 4.

Thus, the battery pack 1 eliminates the need for providing a portionexclusively for connecting the thermostat 9 on the circuit board 4 inaddition to a portion for connecting each of the first electrode lead 5and the second electrode lead 6. It is therefore possible to reducecomponents of the circuit board 4 and simplify a configuration of thecircuit board 4.

Further, since a portion for connecting the second electrode lead 6 isnot required on the circuit board 4, a disposing space for disposingrequired parts and the like on the circuit board 4 can be reduced. Bycorrespondingly reducing size of the circuit board 4, the battery pack 1can be miniaturized.

Further, since the second electrode portions 18 and 18 of the thermostat9 are disposed inside the outline of the other surface 10 c of thecasing portion 10 as described above, a disposing space for disposingthe thermostat 9 on the circuit board 4 can be further reduced, thusfurther miniaturizing the battery pack 1.

It is to be noted that in the description above, the first electrodelead 5 is connected to the first electrode connecting portion 7 of thecircuit board 4 and the second electrode lead 6 is connected to thefirst electrode portion 13 of the thermostat 9; conversely, however, thesecond electrode lead 6 may be connected to the first electrodeconnecting portion 7 of the circuit board 4 and the first electrode lead5 may be connected to the first electrode portion 13 of the thermostat9.

Also, while the description above has shown the battery pack 1 in whichthe battery cell 3 formed by sealing the battery main body portion 3 awith the covering 3 b made of a polymer material is housed within thecasing 2, the present invention is applicable to a battery pack 1Ahousing a battery cell 3A formed by disposing required parts within abattery can 21 formed of an aluminum material, as shown in FIG. 6.

In the battery pack 1A, one end portion of a first connecting lead 22provided as a first electrode lead is connected to a positive electrode(battery can 21) of the battery cell 3A, and one end portion of a secondconnecting lead 23 provided as a second electrode lead is connected to anegative electrode of the battery cell 3A.

Another end portion of the first connecting lead 22 is connected to afirst electrode connecting portion 7 of a circuit board 4, and anotherend portion of the second connecting lead 23 is connected by welding toa first electrode portion 13 of a thermostat 9 connected to a secondelectrode connecting portion 8 of the circuit board 4.

Thus, the battery pack 1A also eliminates the need for providing aportion exclusively for connecting the thermostat 9 on the circuit board4 in addition to a portion for connecting each of the first connectinglead 22 and the second connecting lead 23. It is therefore possible toreduce components of the circuit board 4 and simplify a configuration ofthe circuit board 4.

Further, since a portion for connecting the second connecting lead 23 isnot required on the circuit board 4, a disposing space for disposingrequired parts and the like on the circuit board 4 can be reduced. Bycorrespondingly reducing size of the circuit board 4, the battery pack1A can be miniaturized.

All the concrete shapes and structures of the parts shown in theforegoing embodiments are mere examples of embodiment in carrying outthe present invention; they are not to be construed as restrictive ofthe technical scope of the present invention.

As is clear from the above description, a battery pack according to thepresent invention in which a battery cell and a circuit board having apair of electrode connecting portions are housed in a casing and a pairof electrode leads each connected to a positive electrode or a negativeelectrode of the battery cell is projected from the battery cellincludes a thermostat having a casing portion formed of a nonconductivematerial, a first electrode portion disposed at one surface of thecasing portion, and a second electrode portion disposed at anothersurface opposite to the one surface of the casing portion, wherein oneelectrode lead is connected to one electrode connecting portion of thecircuit board; the other electrode lead is connected to the firstelectrode portion of the thermostat; and the second electrode portion ofthe thermostat is connected to the other electrode connecting portion ofthe circuit board.

Thus, it is not necessary to provide a portion exclusively forconnecting the thermostat on the circuit board in addition to a portionfor connecting each of the one electrode lead and the other electrodelead. It is therefore possible to reduce components of the circuit boardand simplify a configuration of the circuit board.

Further, since a portion for connecting the other electrode lead is notrequired on the circuit board, a disposing space for disposing requiredparts and the like on the circuit board can be reduced. Bycorrespondingly reducing size of the circuit board, the battery pack canbe miniaturized.

Further, in the present invention, the second electrode portion of thethermostat is disposed inside the outline of the other surface of thecasing portion. Therefore a disposing space for disposing the thermostaton the circuit board can be further reduced, thus further miniaturizingthe battery pack.

A thermostat according to the present invention for use in a batterypack in which a battery cell and a circuit board having a pair ofelectrode connecting portions are housed in a casing and one of a pairof electrode leads each connected to a positive electrode or a negativeelectrode of the battery cell is connected to one electrode connectingportion of the circuit board includes a casing portion formed of anonconductive material, a first electrode portion disposed at onesurface of the casing portion and connected with the other electrodelead, and a second electrode portion disposed at another surfaceopposite to the one surface of the casing portion and connected with theother electrode connecting portion of the circuit board.

Thus, it is not necessary to provide a portion exclusively forconnecting the thermostat on the circuit board in addition to a portionfor connecting each of the one electrode lead and the other electrodelead. It is therefore possible to reduce components of the circuit boardand simplify a configuration of the circuit board.

Further, since a portion for connecting the other electrode lead is notrequired on the circuit board, a disposing space for disposing requiredparts and the like on the circuit board can be reduced. Bycorrespondingly reducing size of the circuit board, the battery packusing the thermostat can be miniaturized.

Further, in the present invention, the second electrode portion isdisposed inside the outline of the other surface of the casing portion.Therefore a disposing space for disposing the thermostat on the circuitboard can be further reduced, thus further miniaturizing the batterypack using the thermostat.

1. A battery pack, comprising: a battery cell with a positive electrodeand a negative electrode; a circuit board having first and secondelectrode connecting portions; a battery pack casing in which thebattery cell and the circuit board are housed; first and secondelectrode leads projecting from said battery cell and respectivelyelectrically connected to the positive electrode and the negativeelectrode of the battery cell; and a thermostat having (a) a thermostatcasing a portion of which is formed of a nonconductive material, and (b)first and second electrode portions each having oppositely facingexposed portions at upper and lower major surfaces of the thermostatcasing, the first electrode exposed portion forming a first portion ofthe upper major surface of the thermostat casing, wherein, the firstelectrode lead is connected to the circuit board by the first electrodeconnecting portion, the second electrode lead is connected to theexposed portion of the first electrode portion of the thermostat, theexposed portion of the second electrode portion of the thermostat isconnected to the second electrode connecting portion of the circuitboard such that said thermostat is sandwiched between the secondelectrode lead and second electrode connecting portion of the circuitboard, and the first electrode is partially embedded in the casingportion via a recessed portion therein.
 2. The battery pack as claimedin claim 1, wherein the second electrode portion of said thermostat isdisposed within an outline of an outer perimeter of the thermostatcasing.
 3. A thermostat which can be used in a battery pack, in which(a) a battery cell with positive and negative electrodes and a circuitboard having a pair of electrode connecting portions are housed in afirst casing, (b) there are a pair of electrode leads respectivelyconnected to the positive electrode and the negative electrode of thebattery cell, (c) one of the electrode leads is connected to oneelectrode connecting portion of the circuit board, said thermostatcomprising: a second casing with a portion formed of a nonconductivematerial; a first electrode portion forming one major surface of thesecond casing and connectable with the other electrode lead of thebattery cell; a second electrode portion disposed at another oppositelyfacing major surface of the second casing and connectable with the otherelectrode connecting portion of said circuit board; auxiliary electrodeportions projecting from side edges of the thermostat casing; and endportions of the auxiliary electrode portions formed as auxiliaryelectrode connecting portions, wherein the end portions areperpendicular to the auxiliary electrode portions, wherein saidthermostat is sandwiched between said other electrode of said batterycell and said other electrode connecting portion of said circuit board.4. The thermostat as claimed in claim 3, wherein said second electrodeportion is disposed within an outer perimeter of the second casing. 5.The battery pack as claimed in claim 3, wherein the auxiliary electrodeconnecting portions are bent perpendicularly to be parallel with thefirst electrode portion, and are situated so as to be opposed to a partof another surface 10 c of the casing portion
 10. 6. A battery packcomprising: a battery cell with a positive electrode and a negativeelectrode; a circuit board having first and second electrode connectingportions; a battery pack casing in which the battery cell and thecircuit board are housed; first and second electrode leads projectingfrom said battery cell and respectively electrically connected to thepositive electrode and the negative electrode of the battery cell; athermostat having (a) a thermostat casing a portion of which is formedof a nonconductive material, and (b) first and second electrode portionseach having oppositely facing exposed portions at upper and lower majorsurfaces of the thermostat casing, the first electrode exposed portionforming a first portion of the upper major surface of the thermostatcasing; and a movable piece portion of the first electrode portion thatis bent from one edge of the first electrode portion, wherein, the firstelectrode lead is connected to the circuit board by the first electrodeconnecting portion, the second electrode lead is connected to theexposed portion of the first electrode portion of the thermostat, theexposed portion of the second electrode portion of the thermostat isconnected to the second electrode connecting portion of the circuitboard such that said thermostat is sandwiched between the secondelectrode lead and second electrode connecting portion of the circuitboard, and wherein the movable piece portion is capable of elasticdisplacement with respect to the first electrode portion.
 7. The batterypack as claimed in claim 1, further comprising: second and thirdportions of the upper major surface of the thermostat casing, whereinthe second and third portions are coplanar to the first portion of theupper major surface of the first electrode exposed portion.
 8. Thebattery pack as claimed in claim 7, wherein the second and thirdportions of the upper major surface of the thermostat casing are formedof a nonconductive material.
 9. The battery pack as claimed in claim 7,wherein the first portion of the upper major surface of the firstelectrode exposed portion is situated between the second and thirdportions of the upper major surface of the thermostat casing.
 10. Thebattery pack as claimed in claim 3, further comprising: second and thirdmajor surfaces of the second casing, wherein the second and third majorsurfaces are coplanar to the first major surface of the second casing.11. The battery pack as claimed in claim 10, wherein the second andthird major surfaces of the second casing are formed of a nonconductivematerial.
 12. The battery pack as claimed in claim 10, wherein the firstmajor surface of the second casing is situated between the second andthird major surfaces of the second casing.